Catalytic heater control

ABSTRACT

An electronic control for a catalytic heater device for preheating liquid coolant of an internal combustion engine. The control has a preheat circuit for energizing a resistance wire element for a period of time to heat a catalytic material of the heater device to an operating temperature, a pump circuit for cycling an electric pump to supply liquid fuel to the heater device, and an inhibiting circuit to prevent operation of the electric pump if the heater device is functioning improperly.

United States Patent l 1 1 [111 3,901,213 Charboneau Aug. 26, 1975CATALYTIC HEATER CONTROL Primar Examiner-Edward G. Favors 75 I t: B.Chab ,0, Ct, y l men or J r oneau 155 l y Attorney, Agent, orFirmBarnes, Kisselle, Raisch &

Choate [73] Assignee: Walbro Corporation, Cass City,

57 ABSTRACT Filedi g- 2, 1974 An electronic control for a catalyticheater device for [21] APPL No; 494,207 preheating liquid coolant of aninternal combustion engine. The control has a preheat circuit forenergizing a resistance wire element for a period of time to [52] US. Cl126/350 A; 431/66 heat a catalytic material f the heater device to an[51] Int. Cl. F2411 1/38 erating temperature, a pump circuit for Cyclingan [58] Field of Search 431/66, 208; 126/350 A electric pump to Supply li fuel to the heater vice, and an inhibiting circuit to preventoperation of References Clted the electric pump if the heater device isfunctioning UNITED STATES PATENTS improperly. 3,277,886 Ryals et al AClaims 4 D g ig 3,501,257 3/1970 Hilton et al 126/350 A CATALYTIC HEATERCONTROL This invention relates to a catalytic heater device forpreheating the liquid coolant of an internal combustion engine and moreparticularly to an electronic control for such a device. 7

Objects of this invention are to provide a control for a catalyticheater device which protects the device from becoming damaged if thedevice functions improperly and is compact and of economical manufactureand assembly, and has a long maintenance-free service life.

These and other objects, features, and advantages of this invention willbe apparent from the following description, appended claims, andaccompanying drawings in which:

FIG. 1 is a side view partially in section of a catalytic heater whichis cycled by a control device embodying this invention.

FIG. 2 is a semi-diagrammatic view of the catalytic heater of FIG. 1connected to both a control device embodying this invention and a fuelpump supplying gasoline to the catalytic heater.

FIG. 3 is a sectional view of the fuel pump of FIG. 2.

FIG. 4 is a schematic diagram of an electronic con trol device embodyingthis invention.

Referring in more detail to the drawings, FIG. 1 illustrates a catalyticheater having a heat exchanger jacket 12 encircling a catalytic heaterassembly 14. Heat exchanger 12 has a cylindrical chamber 16 defined byan inner metallic tube 18, an outer metallic tube 20 encircling theinner tube, and metallic end rings 22 interposed between the tubes andfixed thereto, such as by brazing. Engine liquid coolant enters-chamber16 through an inlet conduit 28 fixed to outer tube 20 adjacent the lowerend of chamber 16 and flows from chamber 16 through an outlet conduit 30fixed to outer tube 20 adjacent the upper end of chamber 16. A checkvalve 32 in inlet conduit 28 prevents liquid coolant from flowing out ofchamber 16 through the inlet conduit. A plurality of slots or windows 34and 36 adjacent opposed ends ofinner tube 18 allows atmospheric air toflow through the tube adjacent the outer periphery of heater assembly14.

Heater assembly 14 has a porous ceramic tube 38 with upper and lowerceramic end caps 40 and 42 fixed thereto. A layer of a fibrous material44 is wrapped around ceramic tube 38 and impregnated with a catalyticagent, such as platinum. A suitable fibrous material is the ceramic feltT-3 fiber produced by Refractory Products Company of Carpentersville,III. A nichrome wire 46 extends axially along the outside of the tube 38beneath the layer of fibrous material 44 to provide an electricalresistance heating element for preheating the catalytic heater assembly.One end of nichrome wire 46 is connected to an insulated binding post 48mounted on tube 18 and the other end of wire 46 is connected to tube 18and a ground lead wire 50 by a machine screw 52.

A temperature responsive or thermostatic switch 56 with insulated leadwires 58 and 60 connected thereto is potted on upper end cap 40 by asuitable potting material 56, such as Acid-Alk Mortar No. 33 availablefrom Sauereisen Cements Company of Pittsburgh, Pa. A fuel injector 62with a union 64 and a fuel screen 54 at the upper end of an evaporatortube 66 extends through and is fixed to the upper end of heater assembly14 to discharge vaporized fuel into the interior of ceramic tube 38. Toprevent high winds from extinquishing the catalytic reaction of fuelwith heater assembly 14, a tubular shield 68 on the upper end of heatexchanger 12 extends substantially above exhaust or outlet ports 36.Shield 68 is received over the upper end of outer tube 20 of heatexchanger 12 and retained thereon by a band or hose clamp 70.

To receive and vaporize any liquid fuel discharged from fuel injector132, a secondary evaporator assembly 72 is coaxially received in thelower end of heater assembly 14. Evaporator assembly 72 has anevaporator tube 74 into which droplets of fuel discharged from tube 66are funneled by a flared upper end 76. Evaporator tube 74 is fixed tothe lower end of heater assembly 14, extends through lower end cup 42,and is closed at the lower end thereof by a plug 78 received in a union80 fixed thereto.

Heater assembly 14 is mounted substantially coaxially in heat exchanger12 by an upper locator disc 82 and a lower locator disc 84. Upperlocator disc 82 both bears on the upper end of heater assembly 14 andabuts on three circumferentially spaced, inwardly struck tabs 86 in theupper end of inner tube 18. Heater assembly 14 is yieldably urged intoengagement with upper locator disc 82 by a spring 88 interposed betweenlower locator disc 84 and end cap 42 of the heater assembly. Lowerlocator disc 84 is releasably retained in tube 18 by threecircumferentially spaced tabs 90 received in three circumferentiallyspaced reentrant slots 92 in the lower end of tube 18.

As shown in FIG. 2, when catalytic heater 10 is installed in a motorvehicle, gasoline may be supplied to injector 62 under pressure by aseparate electric fuel pump 94 with an outlet connected by a line 96through a tee 98 to the fuel line 100 of the vehicle (not shown) betweenthe gasoline tank and the fuel pump of the internal combustion engine.The outlet of pump 94 is connected to injector 62 through a fuel line102. As indicated by arrow 104 (FIGS. 1 and 2), catalytic heater 10should be mounted so that the longitudinal axis of heater assembly 14extends generally vertically with fuel injector 62 at the upper endthereof. The catalytic heater 10 is mounted at a vertical height betweenthe vertically highest and lowest points in the cooling system of theengine and preferably closer to the highest point thereof so that theliquid coolant will be circulated by a thermosiphon action through theheater and engine when the heater is operating. The inlet conduit 28 ofheat exchanger 12 is connected by a hose 106 to the engine coolingsystem at a low point thereof such as the engine drain opening orthrough a core plug in the side of the block of the engine. The outletconduit 30 of heat exchanger 12 is connected by a hose 108 to the enginecooling system at a higher point than the inlet 28 such as at theconnection of the heater inlet hose to the cooling system of thevehicle.

The useful life of the catalytic agent of catalytic heater 10 isbelieved to be substantially decreased by contact of the catalytic agentwith liquid fuel, and hence, no fuel should be supplied to the catalyticheater when it is not being operated. However, it has been discoveredthat the main fuel pump of at least some internal combustion enginescreates sufficient pressure surges or pulses in fuel line 90 to forcefuel through conventional electric fuel pumps utilized with catalyticheater 10 and thence into the catalytic heater when it is not operating,thereby decreasing the useful life of the catalytic agent thereof. Thismay be prevented from happening by using conventional valves with aconventional electric pump supplying fuel to the catalytic heater byarranging the valves to prevent fuel from flowing through theconventional pump when the catalytic heater is not operating. However,it is preferred to use a specially designed pump, such as pump 94, witha suitable valve arrangement incorporated directly therein.

As shown in FIG. 3, pump 94 has a housing 110 with a flexible diaphragm112 received therein and underlying a pump chamber 114 in a carrierplate 116 fixed in the housing. Gasoline is admitted to pump chamber 114through inlet conduit 118, inlet valve assembly 120, and passageway 122through carrier plate 1 16 and discharged from the pump chamber throughoutlet passageway 124 in carrier plate 116, outlet valve assembly 126and outlet conduit 128. The gasoline is moved through pump chamber 114by the flexing of diaphragm 112 which is actuated by an armature 130 connected thereto, yieldably biased in one direction by a spring 132, andmoved in the opposite direction by energization of solenoid coil 134.The length of the stroke of armature 130 and hence the quantity of fueldelivered on each discharge stroke of pump 94 is controlled byadjustment of a threaded stop screw 136 received in a nut 138 fixed tohousing 110.

Gasoline is prevented from flowing through pump 94 when solenoid coil134 is de-energized by a valve assembly 140 mounted on carrier plate 116and shown in FIG. 3 in the open position with coil 134 energized. Valveassembly 140 has a valve 142 with a bulbous stem 144 received forreciprocation in a counterbore 146 in carrier plate 116 to close andopen (as shown in FIG. 3) fuel outlet passage 124. Valve 142 has ametallic wear cap 148 on the lower surface thereof and is yieldablybiased by a spring 150 received in an annular pocket 152 into engagementwith armature 130 for reciprocation therewith.

In operation of pump 94 energization of coil 134 moves armature 130 tothe position shown in FIG. 3, thereby opening valve 142 and flexingdiaphragm 112 to pull gasoline into pump chamber 114 through inletconduit 118, inlet valve 120 and passageway 122. When coil 134 isde-energized, spring 132 moves armature 130 upwardly from the positionshown in FIG. 3, thereby moving diaphragm 112 upwardly to discharge fuelfrom pump chamber 114 through passageway 124, outlet valve 126 andoutlet conduit 128, and, upon completion of the discharge stroke ofdiaphragm 112, closing valve 142 against the bias of spring 150. Thus,valve 142 remains closed so long as coil 134 is de energized, therebypreventing gasoline from being forced through pump 94 when the pump isnot operating by pressure surges or pulses in the fuel line 100 to whichinlet conduit 118 is connected.

sembly 14. Control section 172 comprises a comparator 174 having areference input 176 connected through a resistor 178 to bus 160, andhaving a threshold input 180 connected through a resistor 182 to bus 160and through a capacitor 184 to ground 186 of the vehicle frame. A latch188 receives a first input 190 from the output 192 of comparator 174,and a second input 194 from bus 160 directly. Latch 188 has an output196 connected through the anode-cathode junction of a silicon diode 198and thence through a coil 200 of a relay 202 to ground 186. A seconddiode 204 is connected in reverse polarity across coil 200 to suppressinductive ringing in the coil when relay 202 turns off. Relay 202 alsohas a pair of normally open contacts 206, 208 connected to bus 160 andpreheat element 46, and responsive to energization of coil 200 to applybattery power directly to heating element 46.

In the operation of preheat control section 172, the output of latch 188is initially set to a high voltage state by application of battery powerto bus 160. This relatively high voltage forward biases diode 198 sothat relay 202 is energized and preheat current is supplied to element46. At the same time current flows through resistor 182 and intocapacitor 184 so that a charge is In accordance with this invention, acontrol box 156 with an electronic circuit 158 shown schematically inFIG. 10 cycles catalytic heater 10 and fuel pump 94. Power is suppliedto a DC power bus 160 of control circuit 158 from a battery 161 of thevehicle through a fuse 162 and a master power switch 164 with anindicator light 166 connected by lead lines 168, 169 and 170.

Circuit 158 has a preheat control section 172 which is responsive toapplication of battery power to bus 160 to apply power to heatingelement 46 for a predetermined time interval to preheat the catalyst ofheater asgradually built up thereupon. After an interval of timedetermined by the values of resistor 182 and capacitor 184, the voltageon the capacitor at threshold input of comparator 174 exceeds thereference voltage at input 176 so that the comparator provides a resetsignal at input of latch 188. The latch is thus reset so that the outputthereof goes low and relay 202 is deenergized until master switch 164 isturned off and then on again to reset latch 188 to a high voltage state.The preheat time interval determined by resistor 182 and capacitor 184may be in the range of 10 to 15 minutes and is preferably in the rangeof 12 to 14 minutes.

Control circuit 158 further comprises a pump control section 210 whichincludes a first comparator 212 having its reference input 214 connectedthrough a resistor 216 to bus 160, and through series connectedresistors,

218, 220 to ground 186 of the vehicle frame. A filter capacitor 230 isconnected across resistor 220. The threshold input 232 of comparator 212is connected through series connected resistors 234, 236 to bus 160, andthrough a capacitor 238 to ground 186. A second comparator 240 has itsthreshold input 242 connected to threshold input 232 of comparator 212,and has its reference input 244 connected to the junction of resistors218, 220. Resistors 216, 218 and 220 thus form a voltage divider whichplaces a first reference voltage at reference input 214 of comparator212, and a second lower reference voltage at the reference input 244 ofcomparator 240. A resistor 222 and a normally open pushbutton switch areconnected in series across resistor 236. Switch 228 is mounted oncontrol box 156 and may be manually activated to prime pump 94 asexplained in detail hereinafter.

A latch 246 has a first input 248 connected to the output 250 ofcomparator 212, and has a second input 252 connected to the output 254of comparator 240. The output 256 of latch 246 is connected through aresistor 258 to the base of a PNP transistor 260 which has its emitterconnected to bus 160 and its collector connected through the solenoidcoil 134 of pump 94 to ground 186. A diode 262 is connected in reversepolarity across coil 126 to suppress inductive ringing in the coil whentransistor 260 turns ofi. Output 256 of latch 246 is also connectedthrough a resistor 272 to input 176 of comparator 174, and to a firstinput 264 of a discharge switch 266 which has a second input 268connected to the junction of resistors 234, 236 and an out put 270connected to ground 186.

In the operation of pump control section 210, output 256 of latch 246 isset high when battery power is initially applied to bus 160 so that theemitterbase junction of transistor 260 is reverse biased and current isblocked from coil 134 of pump 94. In the meantime current passes throughresistors 236, 234 into capacitor 238 so that the voltage at thresholdinput 232 of comparator 212 gradually rises. When this rising voltageexceeds the reference voltage supplied at input 214 by voltage divider216, 218, 220, comparator 212 supplies a reset input to latch 246 sothat output 256 goes low, transistor 260 conducts and current issupplied to coil 134 of pump 94. At the same time, input 264 ofdischarge switch 266 goes low so that switch 266 discharges capacitor238 through resistor 234 and discharge switch input 268 to ground 186.When the decreasing voltage on capacitor 238 at threshold input 242 ofcomparator 240 drops below the level of the second lower referencevoltage supplied at reference input 244 by voltage divider 216, 218,220, comparator 240 provides a set signal at input 252 of latch 246 sothat the output thereof goes high this turning off transistor 260 andblocking current flow to coil 134 of pump 94. Discharge switch 266 isalso turned off at this time so that capacitor 238 may recharge. Thus,pump control circuit 210 operates as an oscillator which has a periodand duty cycle dependent upon the relative values of resistors 216, 218,220, 234, 236 and capacitor 238. In the preferred embodiment ofcatalytic heater the charge time of capacitor 238 through resistors 236,234 may be in the range of 5 to seconds and preferably is about 10seconds while the discharge time thereof through resistor 234 and switch266 may be in the range of 30 to 80 milliseconds and preferably is about50 to 60 milliseconds Thus, current is supplied to coil 126 of pump 94preferably for 50 to 60 milliseconds at l0-second intervals.

To prime fuel pump 94 a switch 228 is closed to place resistor 222 inparallel with resistor 236, thereby decreasing the charge time forcapacitor 238 and increasing the rate at which pump 94 is cycled. Thedecreased charge time for capacitor 238 when control section 210 isoperating in the pump-priming mode may be in the range of 200 to 700milliseconds and is preferably about 400 to 500 milliseconds.

Control circuit 158 also includes a pump inhibit circuit 274 which isresponsive to the temperature of catalytic heater assembly 14 toselectively inhibit activation of pump control section 210 if heaterdevice 10 is not functioning properly. Circuit 274 includes a first NPNtransistor 276 which has its base connected through a resistor 278 tothe cathode of diode 198, and its emitter connected directly to ground186. The collector of transistor 276 is connected through a resistor 280to bus 160, and to the base of a second NPN transistor 282. The base oftransistor 282 is also connected to ground 186 through normally openthermal switch 56 which is mounted on heater assembly 14 and responsiveto the temperature thereof to connect the base of transistor 282directly to ground. The emitter of transistor 282 vis connected toground and the collector thereof is connected to the junction ofresistor 234 and capacitor 238. Thus, when latch 188 supplies preheatcurrent to element 46, transistor 276 is turned on and transistor 282 isturned off so that capacitor 238 is allowed to alternately charge anddischarge as described above. If heater 10 is operating properly,catalytic heater assembly 14 will be preheated to a temperature at whichthermal switch 56 closes thereby connecting the base of transistor 282to ground independently of preheat section 172 before the preheatsection 172 turns off. However, if the temperature of heater assembly 14is below the temperature at which switch 56 closes when preheat section172 turns off, or if the heater assembly temperature should thereafterfall below such predetermined temperature, switch 56 will be open andcurrent will be supplied to the baseemitter junction of transistor 282through resistor 280. Transistor 282 will then be turned on to drainsubstantially all of the charges from capacitor 238, and to therebyinhibit further operation of pump control section 210 and hence pump 94.

Since the useful life of the catalytic agent is de creased by contactwith liquid fuel, the quantity of liquid fuel supplied to catalyticheater 10 during opera tion thereof should be controlled within closetolerances to assure that an excess quantity of liquid fuel is notsupplied to the catalytic heater. The quantity of liquid fuel suppliedto heater 10 is controlled by adjustment of stop screw 136 of pump 94and the rate of cycling of fuel pump 94 by pump control section 210 ofcontrol circuit 158.

In using catalytic heater 10 to preheat the engine coolant of aninternal combustion engine, master switch 162 is manually actuated toenergize control circuit 158 to supply current to resistance heatingelement 46. Heating element 46 preheats at least portions of thecatalytic agent of heater assembly 14 to an operating temperature whichwould produce a catalytic heat reaction with fuel discharged into theheater assembly. The preheat control section 172 of circuit 158 controlsthe length of time current is supplied to heating element 46 and turnsthe heating element off after sufficient time has elapsed for at leastportions of the cata lytic agent to be heated to an operatingtemperature. Prior to the heating element being turned off by controlsection 172, fuel pump 94 is energized to discharge fuel throughinjector 132 into heating element 14 by the pump control section 210 ofcontrol circuit 158 and, if catalytic heater 10 is functioning properly,temperature responsive switch 56 closes to assure continued cycling ofpump 94 to supply fuel to the catalytic heater. The cyclic or pulsatingflow of liquid fuel supplied by pump 94 to injector 62 is smoothed orevened out by fuel screen 65, at least partially vaporized by evaporatortube 66, and discharged therefrom into heater assembly 14. The vaporizedportion of the fuel under the influence of the catalytic agent of heaterassembly 14 undergoes a catalytic reaction producing heat which warmsliquid coolant in heat exchanger 12. If the fuel is not completelyvaporized by evaporator tube 66, the liquid portion thereof will drop bygravity into secondary evaporator assembly 72 from which it will besubsequently vaporized and discharged into the interior of heaterassembly 14 to undergo a catalytic reaction producing heat to warm theliquid coolant in heat exchanger 12. Liquid fuel is vaporized insecondary evaporator assembly 72 because evaporator tube 74 ismaintained at an elevated temperature by the heat produced by thecatalytic reaction. Heating of the liquid coolant in heat exchanger 12produces a thermosiphon action to circulate the liquid coolant of theengine through heat exchanger 12 and thus preheat the engine tofacilitate starting thereof in cold weather.

I claim:

1. In combination with a catalytic converter of the type in which ahydrocarbon fuel is flamelessly oxidized in the presence of a catalyticmaterial for preheating liquid coolant of an internal combustion engine,a fuel pump to provide said hydrocarbon fuel to said converter, saidfuel pump including activating means responsive to the application ofelectrical power to supply said fuel to said converter, and oscillatorcircuit means responsive to connection to a source of electric power tocyclically apply electric power to said activating means to cycle saidfuel pump.

2. The combination set forth in claim 1 further comprising meansdisposed in heat-transfer proximity to said catalytic material andresponsive to the temperature of said material to disable saidoscillator circuit means if after a predetermined period of time saidtemperature is below a predetermined temperature.

3. The combination set forth in claim 1 wherein said oscillator circuitmeans comprises an electronic switch having first, second and controlelectrodes, said first and second electrodes connecting said pumpactivating means to a source of electric power in response to a controlsignal at said control electrode, and an oscillator connected to asource of electric power to provide said control signal, said oscillatorhaving a first predetermined duty cycle.

4. The combination set forth in claim 3 wherein said first predeterminedduty cycle of said oscillator is effective to apply electric power tosaid energizing means at intervals in the range of 5 to seconds for anamount of time in the range of to 80 milliseconds.

5. The combination set forth in claim 3 wherein said oscillator circuitmeans further comprises means electrically connected to said oscillatorto change the duty cycle thereof from said first duty cycle to a secondhigher duty cycle, said last named means including a switch mechanicallyactivated when priming of said fuel pump is required.

6. The combination set forth in claim 5 wherein said second higher dutycycle is effective to connect said electrical power to said energizingmeans at intervals in the range of 300 to 600 milliseconds for an amountof time in the range of 30 to 80 milliseconds.

7. The combination set forth in claim 1 further comprising a controlcircuit for preheating the catalytic material to a temperature at whichthe catalytic material will react with said hydrocarbon fuel, saidcontrol circuit comprising in combination, an electrical heater elementdisposed in heat-transfer relationship with said catalytic material, andenergizing means to apply electric power to said heater element for afirst predetermined period of time which is independent of thetemperature of said material.

8. The combination set forth in claim 7 wherein said energizing meanscomprises first switch means having an opened and a closed position,said switch means applying power to the remainder of said controlcircuit when in said closed position, and timing means responsive toapplication of said power through said first switch means to energizesaid heater element for said first predetermined period of time.

9. The combination set forth in claim 8 wherein said timing meanscomprises means responsive to closure of said switch means to provide avoltage signal which increases with time from a first to a second level,comparator means having a reference input connected to a source ofelectric power to provide a reference voltage at said reference input, athreshold input electrically connected to said closure responsive means,and an output responsive to reference and threshold inputs, andelectronic switch means responsive to said comparator means to connectsaid heater element to a source of electric power when said thresholdinput is below said reference input and to disconnect said heaterelement from the source of power when said threshold input exceeds saidreference input.

10. The combination set forth in claim 9 wherein said closure responsivemeans comprises a capacitor electrically connected to a source of powerand to said threshold input.

11. The combination set forth in claim 8 further comprising meansdisposed in heat-transfer relationship with said catalytic material andresponsive to the temperature of said catalytic material to disable saidoscillator circuit means if after said first predetermined period oftime said temperature is below a predetermined temperature.

12. The combination set forth in claim 11 further comprising meansresponsive to activation of said preheating control circuit to allowoperation of said oscillator circuit means independently of saidtemperature responsive means for a second predetermined period of time.

13. The combination set forth in claim 12 wherein said secondpredetermined period of time is not greater than said firstpredetermined period of time.

14. The combination set forth in claim 12 wherein said firstpredetermined period of time is in the range of 10 to 15 minutes.

15. In a catalytic converter of the type in which a hydrocarbon fuel isflamelessly oxidized in the presence of a catalytic material forpreheating liquid coolant of an internal combustion engine, a controlcircuit for preheating the catalytic material to a temperature at whichthe material will react with the hydrocarbon fuel comprising incombination, an electrical heater element disposed in heat-transferrelationship with said catalytic material, first switch means having anopened and closed position, said first switch means applying power tothe remainder of the control circuit when in said closed position, meansresponsive to closure of said first switch means to provide a voltagesignal which increases with time from a first to a second level,comparator means having a reference input electrically connected to asource of power to provide a reference voltage at said reference input,a threshold input electrically connected to said closure responsivemeans, and an .output responsive to reference and threshold inputs, andelectronic switch means responsive to said comparator means to connectsaid heater element to the source of power when said threshold input isbelow said reference input and to disconnect said heater element fromsaid power source when said threshold input exceeds said referenceinput.

16. The combination set forth in claim 15 wherein said closureresponsive means comprises a capacitor electrically connected to saidpower source and to said threshold input.

2. The combination set forth in claim 1 further comprising meansdisposed in heat-transfer proximity to said catalytic material andresponsive to the temperature of said material to disable saidoscillator circuit means if after a predetermined period of time saidtemperature is below a predetermined temperature.
 2. IN COMBINATION WITHA CATALYTIC CONVERTER OF THE TYPE IN WHICH A HYDROCARBON FUEL ISFLAMELESSLY OXIDEZED IN THE PRESENCE OF A CATALYTIC MATERIAL FORPREHEATING LIQUID COOLANT OF AN INTERNAL COMBUSTION ENGINE, A FUEL PUMPTO PROVIDE SAID HYDROCARON FUEL TO SAID CONVERTER, SAID FUEL PUMPINCLUDING ACTIVATING MEANS RESPONSIVE TO THE APPLICATION OF ELECTRICALPOWER TO SUPPLY SAID FUEL TO SAID CONVERTER, AND OSCILLATOR CIRCUITMEANS RESPONSIVE TO CONNECTION TO A SOURCE OF ELECTRIC
 3. Thecombination set forth in claim 1 wherein said oscillator circuit meanscomprises an electronic switch having first, second and controlelectrodes, said first and second electrodes connecting said pumpactivating means to a source of electric power in response to a controlsignal at said control electrode, and an oscillator connected to asource of electric power to provide said control signal, said oscillatorhaving a first predetermined duty cycle.
 4. The combination set forth inclaim 3 wherein said first predetermined duty cycle of said oscillatoris effective to apply electric power to said energizing means atintervals in the range of 5 to 15 seconds for an amount of time in therange of 30 to 80 milliseconds.
 5. The combination set forth in claim 3wherein said oscilLator circuit means further comprises meanselectrically connected to said oscillator to change the duty cyclethereof from said first duty cycle to a second higher duty cycle, saidlast named means including a switch mechanically activated when primingof said fuel pump is required.
 6. The combination set forth in claim 5wherein said second higher duty cycle is effective to connect saidelectrical power to said energizing means at intervals in the range of300 to 600 milliseconds for an amount of time in the range of 30 to 80milliseconds.
 7. The combination set forth in claim 1 further comprisinga control circuit for preheating the catalytic material to a temperatureat which the catalytic material will react with said hydrocarbon fuel,said control circuit comprising in combination, an electrical heaterelement disposed in heat-transfer relationship with said catalyticmaterial, and energizing means to apply electric power to said heaterelement for a first predetermined period of time which is independent ofthe temperature of said material.
 8. The combination set forth in claim7 wherein said energizing means comprises first switch means having anopened and a closed position, said switch means applying power to theremainder of said control circuit when in said closed position, andtiming means responsive to application of said power through said firstswitch means to energize said heater element for said firstpredetermined period of time.
 9. The combination set forth in claim 8wherein said timing means comprises means responsive to closure of saidswitch means to provide a voltage signal which increases with time froma first to a second level, comparator means having a reference inputconnected to a source of electric power to provide a reference voltageat said reference input, a threshold input electrically connected tosaid closure responsive means, and an output responsive to reference andthreshold inputs, and electronic switch means responsive to saidcomparator means to connect said heater element to a source of electricpower when said threshold input is below said reference input and todisconnect said heater element from the source of power when saidthreshold input exceeds said reference input.
 10. The combination setforth in claim 9 wherein said closure responsive means comprises acapacitor electrically connected to a source of power and to saidthreshold input.
 11. The combination set forth in claim 8 furthercomprising means disposed in heat-transfer relationship with saidcatalytic material and responsive to the temperature of said catalyticmaterial to disable said oscillator circuit means if after said firstpredetermined period of time said temperature is below a predeterminedtemperature.
 12. The combination set forth in claim 11 furthercomprising means responsive to activation of said preheating controlcircuit to allow operation of said oscillator circuit meansindependently of said temperature responsive means for a secondpredetermined period of time.
 13. The combination set forth in claim 12wherein said second predetermined period of time is not greater thansaid first predetermined period of time.
 14. The combination set forthin claim 12 wherein said first predetermined period of time is in therange of 10 to 15 minutes.
 15. In a catalytic converter of the type inwhich a hydrocarbon fuel is flamelessly oxidized in the presence of acatalytic material for preheating liquid coolant of an internalcombustion engine, a control circuit for preheating the catalyticmaterial to a temperature at which the material will react with thehydrocarbon fuel comprising in combination, an electrical heater elementdisposed in heat-transfer relationship with said catalytic material,first switch means having an opened and closed position, said firstswitch means applying power to the remainder of the control circuit whenin said closed position, means responsive to closure of said firsTswitch means to provide a voltage signal which increases with time froma first to a second level, comparator means having a reference inputelectrically connected to a source of power to provide a referencevoltage at said reference input, a threshold input electricallyconnected to said closure responsive means, and an output responsive toreference and threshold inputs, and electronic switch means responsiveto said comparator means to connect said heater element to the source ofpower when said threshold input is below said reference input and todisconnect said heater element from said power source when saidthreshold input exceeds said reference input.
 16. The combination setforth in claim 15 wherein said closure responsive means comprises acapacitor electrically connected to said power source and to saidthreshold input.